This invention relates to the machining of vulcanized fibre tubing.
Because of its unique properties, vulcanized fibre has become the predominant, or even sole, material from which various items are manufactured. Other of its properties, however, make it a difficult material to machine, especially where high precision is required of the part to be manufactured (e.g., "rotating bands" for artillery shells).
As is well known to those experienced in the machining of vulcanized fibre materials, such materials are difficult to machine with precision for various reasons, including their tendency to deform in response to forces applied by whatever mechanism is employed to hold the vulcanized fibre material (e.g., a lathe chuck). This problem is particularly acute, of course, where close tolerances are required. Heretofore, the manufacture of such parts has involved the feeding of elongated (e.g., 30 inches) tubes of vulcanized fibre through the hollow spindle of a lathe, clamping the tube around the exterior surface with a short (e.g., 3 inch) segment projecting from the chuck, and performing the necessary turning and final cut-off operations with tools supported on a lathe turret. It has been discovered that with this technique the projecting segment of the tube is deformed by the pressure of the chuck jaws. Upon completion of the ring-shaped part and cut-off from the remainder of the tube, the part resumes its original, unstressed configuration. Since the cuts were made in the deformed shape of the material, the resulting part often deviates from the required tolerances.